Gas turbine engines typically include a compressor section for compressing inlet air, a combustion section for combining the compressed air with fuel and combusting the fuel, and a turbine section where the energy from the hot gas produced by the combustion of the fuel is converted into work. The exhaust gas from the turbine section can also be used to achieve thrust or as a source of heat and energy.
Spray nozzles are commonly used to introduce the fuel as droplets into the combustion section. However, another known application for spray nozzles is to introduce water (or other appropriate fluid) as droplets (“fog”) into the compressor inlet air stream to reduce the temperature of the air by evaporation. Fog systems spray ultra-fine water droplets into the inlet duct of the gas turbine. Most droplets evaporate quickly, cooling the inlet air stream, raising mass flow, and boosting turbine capacity. Some droplets pass through the inlet duct and are ingested in the compressor. Typically, the droplets evaporate rapidly inside the compressor, which prevents erosion damage to the compressor components, and which provides an added power boost from the cooling effect.
Such an application, conventionally referred to as “wet compression”, is particularly useful with land-based power generation units, and has been adopted in a number of operations. Resort may be had to U.S. Pat. Nos. 6,216,443 and 5,867,977 for examples and discussion of such power generation units, and the location of such spray nozzles. Also, U.S. Pat. No. 5,121,596 describes using such wet compression technique particularly at the time of starting the turbine to reduce thermal stress and surface oxidation of component parts.
Spray nozzles are also used to clean the turbine blades and other components in the engine during engine operation and/or after shut-down. Compressor blades are also typically provided in the compressor section to compress the inlet air. In such applications, the spray nozzles are used to periodically deliver water (or other appropriate fluid such as a chemical cleaning mixture) as droplets against the turbine blades and other internal compressor components, to remove build-ups of contaminants. U.S. Pat. No. 5,867,977, for example, describes such a cleaning process.
As should be appreciated from the above, spray nozzles have a variety of applications in engines, and in particular gas turbine engines, and much has been done to design spray nozzles which are useful for some if not all of the above applications. With the requirements of the spray nozzles for the different applications being significantly different and sometimes at odds with each other (e.g., the cleaning process generally requires larger liquid droplets, while the cooling process generally requires finer droplets), it has sometimes been necessary to mount various nozzle sets within the engine, with certain nozzles being capable of conducting one function, and other nozzles being capable of conducting other functions. It has been a continuing challenge to develop a single spray nozzle which can be used for more than one application, e.g., as a cooling device to introduce fluid into the engine for cooling purposes, and as a cleaning device to introduce fluid into the engine for cleaning purposes. This can result in a more compact engine design, lower cost for the spray system, and less maintenance and repair, all of which can reduce the overall cost of the engine.
It is therefore believed there is a demand in the industry for such a multi-function spray nozzle, and particularly one which can satisfy the requirements as a cooling device and as a cleaning device. Moreover, it is believed there is a continuing demand for spray nozzles useful for engine applications which are relatively straightforward to manufacture and assemble; and which are replicatable, in that the nozzles are generally alike, and the manufacturing can be closely controlled, so that the efficiency and operation of the nozzles is known.